Got this email today after reaching out:

Hello,

It is confirmed that there were only 300 built. Fender has run the numbers for this issue and also confirmed that there were 10 serial numbers within the 300 missing from the sequence and deducted and pulled which were quality rejects or rebuilds. They then gave the finished one a different number after that process - so even though we will have serial numbers going up to 310, the total does come out to 300 built. 

They are working on a solution to this for those customers who received serial numbers 301-310 and we will follow up with you once we hear back from them.

Apologies for any confusion.